   (let [depth (or depth 0)
         truncate truncate
         max-depth (or max-depth max-total-depth)]
-    (log/debug (str "generate-all:" depth "/" max-depth ":         " (strip-refs spec)))
+    (log/trace (str "generate-all:" depth "/" max-depth ":         " (strip-refs spec)))
     (->>
      (lightning-bolts model spec depth max-depth)
      (filter not-fail?)
-     (map (fn [bolt]
+     (map (fn [bolt] ;; create a map of paths within the bolt to possible complements in the bolt.
             (assoc
              (comp-paths-to-complements bolt (find-comp-paths bolt) model depth max-depth)
              [] [bolt])))

                                        
;; during generation, will not decend deeper than this when creating a tree:
;; TODO: should also be possible to override per-language.
(def ^:const max-total-depth 10)

;; use map or pmap.
(def ^:const mapfn map)

            (do-defaults expression model)))
     (filter not-fail?)
     (map (fn [final]
            (log/trace (str "final: " ((:morph-ps model) final)))
            final)))))

(defn generate
